Mower buyers, take heed !!!

[JDgreen]

A little off topic, but many places advertise electric tools as peak horsepower. That is a measure of the maximum toque an electric motor can develop right before it stalls (quits turning) and burns up. Obviously, you can't run a tool like this all day. I suspect a lot of the mowers were rated the same way, they could make the numbers, but at the expense of excessive fuel comsumption, excessive pollution or shortened engine life. Torque is somewhat meaningless, it is a measure of force, not power. I regularly develop 115 ft-lbs of torque when I tighten the lug nuts on my truck, but I don't think I can mow much grass with a torque wrench. Finally, as one of the racing greats (whose name I forget) said, there is no replacement for displacement. So this is good advice, the smallest motor I've got is a Honda 160 cc on my power washer. My new Toro has a Kohler XT-7, which the Kohler website says is 173 cc and 4.8 horsepower. I'll see how it goes when the grass really takes off.

Not off topic at all...my one year old Yardpro (sold at Menards, it's a silver Husqvarna) has that Kohler XT-7 engine...I LOVE the Kohler, most powerful, fuel efficient, oil tight mower engine I have ever used...it cuts like it's well over 173cc, you will be happy with the performance.

You make a good point about torque, how do they measure it on a mower engine? I torque the lugnuts on my GMC to 110 pounds feet...never thought about how that related to a mower engine output.

Great post !!! :thumbsup:

 

[Grass ala Mowed]

Basically they fit some sort of brake on the engine and try to slow the engine down and measure the force this causes at the end of a known length lever. If the most force an engine can develop at the end of a one foot long lever is 10 pounds, it is developing 10 foot-pounds of torque. Torque times rpm equals horsepower. A diesel engine might only develop 350 horsepower at a maximum rpm of 1800 rpm, but could be north of 1000 foot pounds of torque. A high performance gas engine might make 600 hp at 7000 hp and only 500 foot pounds of torque. The diesel will kick butt in a 30,000 pound truck and the gas engine in a sports car. A lawn mower is closer to the truck in its application, constant heavy load (relative to its size) so torque is theorectically a good measure, but there needs to be some rpm, like I said, it's hard to cut my lawn with my torque wrench, even if I'm developing 15 times the torque of my Toro!

 

[jenkinsph]

A little off topic, but many places advertise electric tools as peak horsepower. That is a measure of the maximum toque an electric motor can develop right before it stalls (quits turning) and burns up. Obviously, you can't run a tool like this all day. I suspect a lot of the mowers were rated the same way, they could make the numbers, but at the expense of excessive fuel comsumption, excessive pollution or shortened engine life. Torque is somewhat meaningless, it is a measure of force, not power. I regularly develop 115 ft-lbs of torque when I tighten the lug nuts on my truck, but I don't think I can mow much grass with a torque wrench. Finally, as one of the racing greats (whose name I forget) said, there is no replacement for displacement. So this is good advice, the smallest motor I've got is a Honda 160 cc on my power washer. My new Toro has a Kohler XT-7, which the Kohler website says is 173 cc and 4.8 horsepower. I'll see how it goes when the grass really takes off.

I am often humored by these electric motor ratings. Most 120v appliances are limited to 1500 watts or 15 amps can't remember which. Just really curious how you get enough power out of an appliance with an 18 ga power cord that says it has 6.0 peak hp. What a load of crap.

 

[JDgreen]

Basically they fit some sort of brake on the engine and try to slow the engine down and measure the force this causes at the end of a known length lever. If the most force an engine can develop at the end of a one foot long lever is 10 pounds, it is developing 10 foot-pounds of torque. Torque times rpm equals horsepower. A diesel engine might only develop 350 horsepower at a maximum rpm of 1800 rpm, but could be north of 1000 foot pounds of torque. A high performance gas engine might make 600 hp at 7000 hp and only 500 foot pounds of torque. The diesel will kick butt in a 30,000 pound truck and the gas engine in a sports car. A lawn mower is closer to the truck in its application, constant heavy load (relative to its size) so torque is theorectically a good measure, but there needs to be some rpm, like I said, it's hard to cut my lawn with my torque wrench, even if I'm developing 15 times the torque of my Toro!

Thanks for explanation...but when I think of the amount of force that mower engine can develop at the end of a 22 inch blade (not quite a foot from the center) it's hard to believe they are only rated at about 7 foot pounds max. I read someplace that the impact of getting a hand or foot hit by a spinning mower blade is as much as being hit by a pistol bullet. Don't think I'd want to compare the two first hand...

 

[Grass ala Mowed]

JDGreen - Thats the speed part. The tip of a 22 inch mower blade will travel 5 3/4 feet per revolution. At 3600 rpm that's 60 revolutions per second or 345 feet/second, which is roughly 235 mph and the blade weighs a lot more than a pistol bullet.

jenkinph - You're right, with no losses, it takes 746 watts to make 1 horsepower. Fifteen amps at 120 volts is 1800 watts or slightly less than 2 1/2 horsepower. It takes a few seconds for most circuit breakers to trip, they usually have an inverse current/time curve, the higher the overload, the quicker the trip. So, for an instant, you can exceed the breaker's trip rating and easily develop over 3 horsepower. If you persist, the breaker trips. If you're on a 20 amp breaker, the motor will burn up and protect the breaker from tripping. (BTW, a new motor for a Craftsman 1 1/2 hp table saw costs roughly $125.)

 

[handirifle]

Torque is somewhat meaningless, it is a measure of force, not power. I regularly develop 115 ft-lbs of torque when I tighten the lug nuts on my truck, but I don't think I can mow much grass with a torque wrench.

I disagree. Torque is what does the work, not HP. My tractor with 16hp (diesel) has WAY more power than my lawnmower with 20 (gas). It's all about the torque. The diesel puts out about twice the torque of my gas engine. Kinda like the guys that pull a boat with a diesel vs a guy that uses a gas engine. Both can do fine on the flats, but put them in the hills and the diesel will walk away from the gas truck, and get better mileage doing it, because of torque.

If the mower "A" has the same displacement as mower "B" with higher torque, mower "A" will bog down big time as soon as you hit the higher grass with it.

I am somewhat new to this forum, but see some complaining about lawyers making money on the lawsuits, and yet this forum allowed someone else to post, yet another, class action lawsuit about power claims. All this for the grand payout of $35, whoopee

Keep that up and they won't have to worry about claims, except the claim for bankruptcy. It "torques" me to see a lawsuit about a mower engine that's rated 6hp and puts out 5.1. Do these same clowns pull the engine on their cars to do the same?

That's the way to drive even more jobs offshore, sue the few companies left that sell here. I had been wondering why the canadian, Kubota, web site shows way more info, including prices, than the USA site. Most likely they don't want to get sued over some small typo of an error on the specs.

 

[Grass ala Mowed]

Torque is a measure of force. Horsepower is a measure of work. Horsepower is foot pounds in a given amount of time. Newton figured that a strong horse could raise 550 pounds one foot (550 foot pounds) in one minute. I don't disagree with you, there are two ways to make horsepower, lots of cubic inches and torque or lots of rpm. As I already said, I don't want to go drag racing with a 350 hp, 1000 foot pound diesel nor do I want to pull a semi trailer with a 500 hp 8000 rpm small block chevy. Finally, with the exceptions of gross negligence, lawyers are a waste of whatever. For that matter, so are companies that make extreme claims about their products.

BTW, my work involves large diesel generators, rated around 6000 hp and displacing 1045 cubic inches per cylinder (Colt Peilstick PA6B-16). We're replacing the little ones that only have 645 cubic inches per cylinder (EMD 645-16)!

 

[twall]

I have heard the argument FOR the manufacturers was they were either using SAE or net (one is higher), and they had the option of using either.

I guess they lost because they didn't tell anyone which standard they were using, and the conditions........but they probably were just inflating the dam things as well, citing a new magical way of coming up with bigger numbers. Heck the governments (federal, state, and local) do that all the time......how 'bout a class action lawsuit against them?

 

[deecie]

I am about to buy a mower after using a Craftsman 6.6 hp self-propelled mower for 8 yrs that cost $400. back then. Now, I'm looking at a Troy Bilt that's push only with 5.5 pound torque. I haven't the slightest idea how much power that is, though all 8 reviews were great. Now, I'm confused with the above chart saying this mower has less power than the 4.5 hp one I had 15 yrs ago. At my age 68, I'd like one that's not too hard to push. Wouldn't the lower #s make it a bit lighter? My son refuses to mow every weekend, so I just might do it myself -Think I should I go for it? It's only $200. or bite the bullet for self-propelled?

 

[Mad Mackie]

You can thank a bunch of lawyers in IL and WI for the engine manufacturers not indicating the HP on small engines. All the small engine manufacturers were involved in this suit and Briggs & Stratton payed out 51 million dollars to this suit, they were the biggest. Having been a new Briggs & Stratton engine purchaser several years back I received a notice from the court handling this suit giving me the option to be part of it. Having purchased two engines within the time frame, an 8.5 HP and an 18 HP I was entitled to a wopping $40!!!! I chose to pass on this large amount of cash and not get involved with the nit picking bunch of thieves, the lawyers I mean!!!!!! I've never met a lawyer that admitted that he or she could have been wrong about something!!!!
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Mad Mackie in Taxonnecticut